The Lucky Strike segment at the Mid‐Atlantic ridge, characterized by a well‐defined median valley with a central volcano, is an archetypical slow‐spreading ridge segment and hence an ideal site for studying magmatic and tectonic processes at slow‐spreading ridges. Here we present fine‐scale velocity models of this segment, by applying full waveform inversion to wide‐angle seismic data, that allows characterization of crustal accretion processes along the entire segment. Along ridge axis, the crust thins from ∼8.4 km at the center of the segment to ∼3.7–4.1 km at the segment ends. This large variation in crustal thickness is mainly accommodated by lower crustal thinning toward the segment ends. The ratio of the lower/upper crust thickness varies from 2.2 at the segment center to 0.1 at the segment ends, so upper crust at segment ends accounts for ∼90% of the crustal thickness, suggesting that the lateral dyking is the primary crustal accretion mechanism. The reduction of lower crustal velocity at the segment center indicates the presence there of melt within the lower crust, which is the source of melt delivery for dyke propagation. The upper crustal velocity gradually decreases from the segment center to segment ends, consistent with an increase in faulting and the presence of more evolved magma toward the segment ends. These observations demonstrate the presence of focused magma supply to the segment center. Off‐axis, the upper crustal thickness shows little variation over ∼30 km on both flanks, suggesting the current magmatic accretion mode could have been active for 3 Myr. Plain Language Summary: The Lucky Strike segment at 37°N on the Mid‐Atlantic ridge is characterized by a well‐defined median valley and a volcano at the segment center. Studying the structure of crust formed along this segment is critical for understanding the magmatic and tectonic processes at slow‐spreading ridges. We present fine‐scale crustal structures of the Lucky Strike segment obtained by performing full waveform inversion (FWI) of controlled‐source seismic data recorded by oceanic bottom seismometers. FWI is an advanced seismic imaging technique that constrains the velocity of subsurface by fitting the modeled waveform with the waveform of field data. The crustal thickness along axis decreases from ∼8.4 km at segment center to ∼3.7–4.1 km at segment ends. This variation is mainly due to the thinning of lower crust toward segment ends. This observation demonstrates that the melt is focused to the Lucky Strike segment center and the crust at segment ends is mainly composed of upper crust formed by lateral dyking of melt from the segment center. The across‐axis crustal structure shows little variations over ∼30 km distance on both flanks, suggesting that enhanced melt supply at segment center is not a transient feature on slow‐spreading ridges but can persist for several million years. Key Points: Crust thins by 4.3–4.7 km from the center to the ends of the Lucky Strike segment, indicating a focused melt supply to the segment centerLarge variation in crustal thickness along‐axis is mainly accommodated by a significant thinning of the lower crust toward the segment endsSmall variation in crustal structure across the ridge axis suggests the current magmatic accretion mode has lasted for 3 Myr [ABSTRACT FROM AUTHOR]

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